Bauxite | The Aluminum Association Bauxite Quick Read Bauxite ore is the world’s primary source of aluminum. The ore must first be chemically processed to produce alumina (aluminum oxide). Alumina is then smelted using an electrolysis process to produce pure aluminum metal. Bauxite is typically found in topsoil located in various tropical and subtropical regions. The ore is acquired through environmentally responsible strip-mining operations. Bauxite reserves are most plentiful in Africa, Oceania and South America. Reserves are projected to last for centuries. Take-Away Facts Aluminum must be refined from ore Although aluminum is the most common metal found on Earth (totaling 8 percent of the planet’s crust), the metal is too reactive with other elements to occur naturally. Bauxite ore, refined through two processes, is the primary source of aluminum. Land conservation is a key industry focus An average of 80 percent of the land mined for bauxite is returned to its native ecosystem. Topsoil from the mining site is stored so it can be replaced during the rehabilitation process.

Reserves will last for centuries Although demand for aluminum is increasing rapidly, bauxite reserves, currently estimated at 40 to 75 billion metric tons, are projected to last for centuries. Guinea and Australia have the two largest proven reserves. A wealth of bauxite reserves Vietnam may hold a wealth of bauxite. In November 2010, the prime minister of Vietnam announced the country’s bauxite reserves may total up to 11 billion tons. Bauxite 101 Bauxite ore is the world’s main source of aluminum Bauxite is a rock formed from a reddish clay material called laterite soil and is most commonly found in tropical or subtropical regions. Bauxite is primarily comprised of aluminum oxide compounds (alumina), silica, iron oxides and titanium dioxide. Approximately 70 percent of the world’s bauxite production is refined through the Bayer chemical process into alumina. Alumina is then refined into pure aluminum metal through the Hall–Héroult electrolytic process. Mining bauxite Bauxite is usually found near the surface of terrain and can be strip-mined economically. The industry has taken a leadership role in environmental conservation efforts.

When the land is cleared prior to mining, the topsoil is stored so it can be replaced during rehabilitation. During the strip-mining process, bauxite is broken up and taken out of the mine to an alumina refinery. Once mining is complete, the topsoil is replaced and the area undergoes a restoration process. When the ore is mined in forested areas, an average of 80 percent of the land is returned to its native ecosystem. Production and reserves More than 160 million metric tons of bauxite are mined each year. The leaders in bauxite production include Australia, China, Brazil, India and Guinea. Bauxite reserves are estimated to be 55 to 75 billion metric tons, primarily spread across Africa (32 percent), Oceania (23 percent), South America and the Caribbean (21 percent) and Asia (18 percent). The United States has small amounts of bauxite ore located in Arkansas, Alabama and Georgia. However, very little mining is done in the United States today. Looking forward: Continued improvement in environmental restoration efforts Environmental restoration goals continue to advance. A biodiversity-restoration project under way in Western Australia provides a leading example.

The goal: to reestablish the equivalent level of plant species richness in rehabilitated areas equal to the un-mined Jarrah forest. (A Jarrah forest is tall open forest. Eucalyptus marginata is the dominant tree.) Les Baux, the Home of Bauxite Bauxite was named after the village of Les Baux by Pierre Berthe. This French geologist found the ore in nearby deposits. He was the first to discover that bauxite contained aluminum. Nearly 75 percent of all aluminum ever produced is still in use today. Infinitely recyclable and highly durable, nearly 75 percent of all aluminum ever produced is still in use today. Aluminum is 100 percent recyclable and retains its properties indefinitely. Aluminum is one of the only materials in the consumer disposal stream that more than pays for the cost of its own collection. The Aluminum Association How is aluminum obtained? | Reference.com How is aluminum obtained? A: Quick Answer Aluminum is extracted from bauxite ore using chemical processes. Bauxite is strip mined from near the surface of the earth. The ore is then heated along with a sodium hydroxide solution that chemically separates the aluminum from the ore.

After its separation, it is heated, becomes molten, then electrified, and finally solidified as a solid and wholly aluminum product. Full Answer Aluminum is the third most abundant element, behind oxygen and silicon, and the most abundant in the earth’s crust. It is the second most malleable metal behind gold and is rarely strong enough to be used alone so it is mixed with smaller quantities of manganese, magnesium, silicon, copper, and other metals to strengthen it. Currently aluminum is used in construction, in packaging, and heavily in house hold cookware. Aluminums largest market is the automotive industry. Australia is the producer of the largest amount of bauxite in the world. Although aluminum is present in dyes, food, and antiperspirants, there is little evidence of it being a risk to healthy adults. The ancient Greeks and Romans used aluminum for textile dyeing and as an astringent for wound dressing. A ruby is a gemstone that consists of the element aluminum oxide with some aluminum atoms being replaced by chromium atoms.

extraction of metals - introduction THE EXTRACTION OF METALS - AN INTRODUCTION This page looks at the various factors which influence the choice of method for extracting metals from their ores, including reduction by carbon, reduction by a reactive metal (like sodium or magnesium), and by electrolysis. Details for the extraction of aluminium, copper, iron and titanium are given in separate pages in this section. From ore to metal What are "ores"? An ore is any naturally-occurring source of a metal that you can economically extract the metal from. Aluminium, for example, is the most common metal in the Earth's crust, occurring in all sorts of minerals. However, it isn't economically worthwhile to extract it from most of these minerals. Instead, the usual ore of aluminium is bauxite - which contains from 50 - 70% of aluminium oxide. Note: We always treat bauxite as if it was aluminium oxide for chemistry purposes, although it is actually more complicated than that in reality. Copper is much rarer, but fortunately can be found in high-grade ores (ones containing a high percentage of copper) in particular places. Because copper is a valuable metal, it is also worth extracting it from low-grade ores as well.

Ores are commonly oxides - for example: bauxite chalcopyrite CuFeS2 . . . and a whole lot of other things as well which we won't actually come across as a part of this topic for UK A level purposes. Concentrating the ore This simply means getting rid of as much of the unwanted rocky material as possible before the ore is converted into the metal. In some cases this is done chemically. For example, pure aluminium oxide is obtained from bauxite by a process involving a reaction with sodium hydroxide solution. This is described in detail on the aluminium page in this section. Some copper ores can be converted into copper(II) sulphate solution by leaving the crushed ore in contact with dilute sulphuric acid for a long time. Copper can then be extracted from the copper(II) sulphate solution. But, in many cases, it is possible to separate the metal compound from unwanted rocky material by physical means. A common example of this involves froth flotation. Froth flotation The ore is first crushed and then treated with something which will bind to the particles of the metal compound that you want and make those particles hydrophobic. "Hydrophobic" literally means "water fearing".

In concentrating copper ores, for example, pine oil is often used. The pine oil binds to the copper compounds, but not to the unwanted rocky material. The treated ore is then put in a large bath of water containing a foaming agent (a soap or detergent of some kind), and air is blown through the mixture to make a lot of bubbles. Because they are water-repellent, the coated particles of the metal compound tend to be picked up by the air bubbles, float to the top of the bath, and are allowed to flow out over the sides. The rest of the rocky material stays in the bath. Reducing the metal compound to the metal Why is this reduction? At its simplest, where you are starting from metal oxides, the ore is being reduced because oxygen is being removed. However, if you are starting with a sulphide ore, for example, that's not a lot of help! It is much more helpful to use the definition of reduction in terms of addition of electrons. To a reasonable approximation, you can think of these ores as containing positive metal ions. To convert them to the metal, you need to add electrons - reduction. Note: In some compounds the metal may not literally be present as a positive ion.

Instead, it may be part of a covalent bond - but will always be the least electronegative element present, and so will carry some degree of positive charge. That means that its oxidation state will always be positive. Reducing that oxidation state to zero (in the raw element) will always involve adding electrons. If you aren't sure about oxidation states you could follow this link to find out about them. If you choose to follow this link, use the BACK button on your browser to return to this page later. Choosing a method of reduction There are various economic factors you need to think about in choosing a method of reduction for a particular ore. These are all covered in detail on other pages in this section under the extractions of particular metals. What follows is a quick summary. You need to consider: the cost of the reducing agent; energy costs; the desired purity of the metal. There may be various environmental considerations as well - some of which will have economic costs. Carbon reduction Carbon (as coke or charcoal) is cheap. It not only acts as a reducing agent, but it also acts as the fuel to provide heat for the process.

However, in some cases (for example with aluminium) the temperature needed for carbon reduction is too high to be economic - so a different method has to be used. Carbon may also be left in the metal as an impurity. Sometimes this can be removed afterwards (for example, in the extraction of iron); sometimes it can't (for example in producing titanium), and a different method would have to be used in cases like this. Reduction using a more reactive metal Titanium is produced by reducing titanium(IV) chloride using a more reactive metal such as sodium or magnesium. As you will see if you read the page about titanium extraction, this is the only way of producing high purity metal. The more reactive metal sodium releases electrons easily as it forms its ions: These electrons are used to reduce the titanium(IV) chloride: Note: This is a good example of a reduction in which the metal isn't originally present as an ion. Titanium(IV) chloride is a covalent liquid. The reduction is from titanium in the +4 oxidation state to the metal in the zero oxidation state. The downside of this is expense. You have first to extract (or to buy) the sodium or magnesium.

The more reactive the metal is, the more difficult and expensive the extraction becomes. That means that you are having to use a very expensive reducing agent to extract the titanium. As you will see if you read the page about titanium extraction, there are other problems in its extraction which also add to the cost. Reduction by electrolysis This is a common extraction process for the more reactive metals - for example, for aluminium and metals above it in the electrochemical series. You may also come across it in other cases such as one method of extracting copper and in the purification of copper. During electrolysis, electrons are being added directly to the metal ions at the cathode (the negative electrode). The downside (particularly in the aluminium case) is the cost of the electricity. An advantage is that it can produce very pure metals. Questions to test your understanding If this is the first set of questions you have done, please read the introductory page before you start. You will need to use the BACK BUTTON on your browser to come back here afterwards. How Is Aluminium Extracted From Bauxite Ore? - highettmetal.com.au June 2012 How Is Aluminium Extracted From Bauxite Ore?

Did you know that aluminium as we know it is not found like this naturally? Even though this handy material is found in over 250 different mineral compounds, it has to be extracted from bauxite, an ore that is mined worldwide. The process to extract the aluminium from its ore is a seemingly complex and time consuming one, and it goes as follows: Bauxite Mining The first step in the process is to mine the bauxite from the earth, mostly from underground deposits (the largest ones can be found in Southern Europe and Hungary). The bauxite is blasted loose and washed to remove any excess clay. Bayer Process The second step is known as the Bayer process, which involves a combination of a chemical extraction and a mechanical separation to extract alumina (the base from of aluminium) from the bauxite. In the first step of the process, the alumina is released from the bauxite when it is crushed and dissolved in sodium hydroxide. The resulting solution travels through a number of filters and separators to remove insoluble particles (leaving a liquefied sodium aluminate). In the second step, the alumina is recovered from this solution when it crystallizes in a precipitation tank.

The alumina settles on the bottom, is dried and ground into a find white powder that can be further refined into metallic aluminium. As you can see, the process used to extract aluminium from the bauxite ore it originates in is fairly complex and requires a number of different machines in order to be completed. Whilst the biggest aluminium manufacturing plants are located in Europe, they do exist here in Australia, just not on the same large scale due to our smaller deposits. Aluminium is a light weight, silver-grey metal obtained from bauxite ore in a two stage process ALUMINIUM MAKING & RECYCLING Aluminium is a light weight, silver-grey metal obtained from bauxite ore in a two stage process. In the first (chemical) stage, crushed bauxite is mixed with a hot solution of caustic soda which dissolves the alumina (aluminium oxide). Undissolved sand and mud, together with any other impurities, are filtered out and the caustic solution is then cooled to crystallize the dissolved alumina into a white, sandy powder. In the second, (smelting) stage, alumina is dissolved at temperatures of around 900 degrees centigrade.

A powerful electric current is passed through the liquid and this splits the aluminium oxide into its two constituents: aluminium and oxygen. Molten aluminium is drawn off and cast into ingots. Aluminium is the third most abundant element (the first two are oxygen and silicon), and the most abundant metal, in the earth's crust, of which it makes up about eight per cent by mass. Aluminium is non-magnetic and a good conductor of electricity. It oxidizes easily, the layer of oxide on its surface making it highly resistant to corrosion. Because of its corrosion resistance as well as its light weight, aluminium is today widely used in ship-building and aircraft manufacture. It is also used in cables, cars, windows and doors, to make foil, and for domestic applications such as cooking utensils and drinks cans. Aluminium sulphate is used as a coagulant in water treatment, to collect impurities suspended in the water. When it was first identified at the beginning of the nine tenth century, it was so difficult to extract it was considered a semi-precious metal. The pure metal was not readily available until the middle of the nineteenth century.

In its pare state, aluminum is soft and quite weak, but when alloyed with other elements such as copper or silicon it becomes very strong. Mining Bauxite is the principal ore of aluminum. It is formed by the chemical weathering of rocks in tropical climates. Chief producers of bauxite are Australia, Jamaica, Russia, Kazakhstan, Surinam and Brazil. Bauxite is recovered in open cast mines, and the chemical processes which separate the alumina leave in their wake large amounts of residues, known as red mad because of the iron compounds which colour it. Making one tonne of pure aluminum requires the extraction of four tonnes of bauxite. As with all primary metal extraction and refining processes, production generates significant quantities of solid wastes. Energy Intensive A lot of energy is needed to produce aluminium: around 146 Megajoules per kilogram (Mj/kg), compared to 32 Mj/kg for steel and 90 Mj/kg for plastic such as polythylene. Efficiencies in the industry have reduced energy consumption by around 30 per cent in the last 50 year.

However, aluminium production must be located in areas where cheap energy sources, such a hydro-electricity, are available if it is to be economically viable. EDDY CURRENT SEPARATION Although it is not magnetic, a magnetic effect can be induced in aluminium by the application of a strong fluctuating magnetic field. This causes a small electric current in the aluminium and an associated magnetic field which is opposed to the applied magnetic field, enabling the aluminum to be separated. Eddy current separation of aluminium cans from steal cans, or from a mixed waste stream, is widely used at waste sorting plants: more than 200 units are already operating in waste processing facilities and incinerators across Europe. Benefits There are a number of benefits associated with the substitution of aluminium for other, more traditional materials. For example, its use for motor vehicle engines and other parts greatly reduces the weight of the car, reducing the vehicle's fuel consumption and therefore its overall environmental impact. On average, around five to ten per cent of a current model might be aluminium.

However, there have been some aluminium-intensive experiments by car makers: the aluminium body of the Audi A8 is 40 per cent lighter than the typical steel car body, and because of its rust resistance, it also has a longer life expectancy. Aluminium is used to make durable, low-maintenance window and door frames for buildings, replacing wood which, while a renewable material, has to be extensively treated with chemicals (such as fungicides) and painted to slow the rotting process. Aluminium in the waste stream Aluminium scrap generated in industrial manufacturing processes is always recycled because of its high value. The US aluminium industry claims that Americans have earned around US$9 billion in can recycling since the 1970s. There is very little aluminium in the household waste stream - less than one per cent of the waste and around two per cent of the recyclables (but around 50 per cent of the value). Almost all of this comes from drinks cans. A tiny amount comes from aluminium foil, used in the home for cooking and wrapping foods, and by the food industry for lids on dairy products (such as cream and yogurt), pie cases, and for containers for ready-prepared meals and take-away foods.

Additionally, a very thin layer of aluminium foil (around five microns) is sandwiched between layers of other materials, such as paper and plastic, to make a laminated packaging material for coffee, long-life milk, juice and other items. The aluminium is used because it forms a very effective barrier. The aluminium that arises from other sources (such as car parts or old saucepans) is handled by scrap metal dealers. THE RING PULL First invented in the 1960s in the USA, drinks cans with ring pulls for ease of opening rely on the softness of aluminium. Whether the body (including the base) of the can is steel or aluminium, the top which carries the ring-pull is always made from aluminium. Even all-aluminium can use a different mix of alloys: the body of the can is in alloy of aluminium, manganese and magnesium, while the top and ring pull (called the stay-on-tab within the industry), are alloyed in different proportions Re-use & recycling Very little aluminium is reused, without re-smelting, but one exception to that is the beer keg. Aluminium recycling is cost effective simply because of the high energy input needed for the raw material.

Using recycled cans to produce new ones allows industry to make up to 20 times more cans for the same amount of energy. In America, aluminium can recycling saved more than 18 million barrels of oil in 1996. Even long distance haulage to recycling facilities - which for many materials obviates the environmental benefits of recycling - is not enough to cancel the relative benefits. Recycling any material reduces virgin resource consumption. Where that virgin resource is a metal, there is a resulting reduction of mining, with its associated impacts. A further boost to aluminium recycling (like that for steel) is the guaranteed reprocessing capacity, and a guaranteed market for the re-processed material. Shortage of reprocessing capacity and fluctuating end-use markets for other materials, such as paper, limit recycling. While the price paid for collected aluminium does vary, it remains higher than for other materials. In Europe, the aluminium can recycling rate reached 40 per cent in 1997 (more than 75,000 tonnes of used cans), up from 37 per cent in 1996 and 30 per cent in 1994.

The overall rate is expected to exceed 50 per cent by 2000. ALUMINIUM DRINKS CANS In 1997 more than 15 billion aluminium drinks cans were sold in Europe alone, around 50 per cent of the total cans sold. The first aluminium beverage can in the USA (in 1935) weighed almost 100 grammes (g), almost six times heavier than those used in the present day. When first used for drinks cans, the aluminium was several times lighter than the steel it replaced, and there were major energy savings in distribution. Recent developments in steel technology have greatly reduced the thickness of steel needed to make cans (as well as replacing the lid with aluminium), but there is still a significant weight difference: a 330 ml can in steel weighs around 30 g while the aluminium equivalent weighs around 15 g. Reverse vending machines were proposed (for instance in Sweden) combined with deposits, as a way to get back more aluminium cans for recycling. An empty can dropped into the slot prompted the machine to pay out a coin or a voucher in return.

While the machines attract the return of cans, especially from children, maintaining and servicing the machines is expensive, as are the machines themselves, and the technology has not spread widely. Depending on the efficiency of the process, up to 90 per cent of the energy used to make a can from virgin material can be saved by recycling. There are some losses in the melting process, and also some limitations caused by the different alloys. Paints and lacquers on the used cans are burned off in the re-melting process. The industry claims a world-wide recycling rate of 55 per cent for aluminium drinks cans. For Europe, that figure is 40 per cent (see Table opposite). In the UK alone, 1.5 billion cans - amounting to 23,900 tonnes - wore collected for recycling in 1997. Aluminium foil is no harder to recycle, but it is harder to collect for recycling as it occurs in smaller quantities. It may also be contaminated with food. Laminated materials can in principle be recycled but in practice they often are not, because of the high costs involved in separating the different component parts.

Despite this non-recyclability, laminated materials need not be detrimental to the environment as they reduce the total amount of materials needed in manufacture (several thin layers each performing different purposes replacing one thick layer), and their light weight reduces transport costs and impacts. Some laminated products do not need refrigeration, saving energy. Conclusions Aluminium's light weight and corrosion-resistant qualities make it a useful material in a number of applications. Because of the environmental impacts associated with the acquisition and production of car WRF January 1999, recycling it has considerable benefits. THE DANISH BAN In the late 70s, Denmark introduced a ban on the sale of beer and soft drinks in cans, ostensibly for environmental reasons although many believed it was to protect its national beer industry. By banning one-way cans and requiring refillable bottles, Denmark disadvantaged beer importers from countries like Germany: returning bottles to Germany for washing and refilling was not viable. The fact that Denmark continued to export its own beers in cans was widely resented. The European Commission has challenged Denmark s ban, and the Danish Environmental Protection Agency published a life cycle assessment which defended the current Danish policy.

Aluminium - Fact Sheets - Australian Mines Atlas Suggestions for Further Reading Introduction Aluminium (Al) comprises about 8.2% of the Earth's crust. It is the third most abundant element in the crust and the most plentiful metallic element, but is never found on its own in nature. Bauxite is the ore most commonly mined for aluminium in which aluminium occurs as hydroxide minerals. Aluminium is a silvery-white, tough and lightweight metal (specific gravity 2.7). It is a good conductor of heat and electricity, is very resistant to atmospheric corrosion (it never rusts), is nontoxic, inflammable, nonmagnetic and non-sparking, and it is malleable and ductile. Because of these properties it has become an important metal. Metallic aluminium was first isolated in 1825 by Hans Christian Oersted from aluminium chloride but it was not commercially produced until 1888 with the establishment of the Pittsburgh Reduction Company (known as Alcoa since 1907). Aluminium can be mixed with almost any other metal and these alloys typically combine lightness with strength. As a result, they are used in a great variety of industries.

In Australia, aluminium is produced in Tasmania, Queensland, Victoria and New South Wales with the building and construction industries being the most important consumers. Occurrence In 1821, French geologist Pierre Berthier discovered an aluminium-rich material near the village of Les Baux in Provence, France. It was named bauxite after the village. Bauxite occurs as a weathered cover or blanket, known as laterite or duricrust, over a variety of alumina-bearing rocks. It forms when large amounts of rainfall leach away the more mobile elements in the host rock leaving the relatively immobile aluminium with some silicon, iron and titanium. Because of the way it forms, bauxite deposits can be very extensive and are found on almost every continent. The largest known economic resources occur in Guinea and Australia, followed by Brazil, Vietnam and Jamaica. The main aluminium minerals in bauxite are gibbsite [Al(OH)3, also written as Al2O3.H2O in oxide notation], boehmite [AlO(OH), written as Al2O3.H2O in oxide notation] and diaspore, which is a polymorph of boehmite but is denser and harder.

Pure alumina (Al2O3) contains 52.9% aluminium and 47.1% oxygen. Bauxite may be as hard as rock or as soft as mud and may occur as compacted earth (both friable and re-cemented), small balls (pisolites), or hollow, twig-like material (tubules). Its colours may be buff, pink, yellow, red, or white, or any combination of these. Bauxite ore refers to bauxite that contains sufficiently high levels of Al2O3 and suitably low levels of iron oxide (Fe2O3) and silica (SiO2) to be economically mineable. The amount of reactive silica is particularly important as this form of silica consumes the caustic soda needed to make alumina, thus low reactive silica is desirable. Other potential sources of aluminium include a variety of rocks and minerals such as aluminous shale and slate, aluminium phosphate rock and high-alumina clays. Australian Resources and Deposits In 2014, Australia was the world’s largest producer of bauxite (30%) and the second largest producer of alumina (19%).

Bauxite is mined from established open cut operations at Weipa in Queensland, Gove in the Northern Territory and the Darling Range in Western Australia. Additionally, new mines have begun operation in the Cape York region of Queensland and in central Tasmania. Other bauxite deposits occur in northern Western Australia, New South Wales and eastern Queensland but are currently uneconomic to mine. Australia's bauxite resources are assessed each year by Geoscience Australia. The assessment is based on published and unpublished data. These estimates are published each year in Australia’s Identified Mineral Resources . Once mined, the next stage in aluminium production is the chemical Bayer Process where alumina (Al2O3) is extracted from bauxite in a refinery. Australia has six alumina refineries: QAL and Yarwun are located in Queensland near Gladstone, and Kwinana, Pinjarra, Worsley and Wagerup are all located in Western Australia in the Darling Range. The final stage of aluminium production takes place in a smelter. The electrochemical Hall-Héroult Process uses huge amounts of power to extract aluminium metal from alumina.

(Aluminium is sometimes referred to as ‘solid electricity’ owing to the large amount of power used in its production.) Australia has four aluminium smelters: Bell Bay in Tasmania, Boyne Island in Queensland, Portland in Victoria and Tomago in New South Wales. In 2014, Australia produced the largest amount of bauxite in the world followed by China, Brazil, India and Guinea and the second largest amount of alumina after China. China is the world’s largest consumer of aluminium and, despite strong domestic production, imports large amounts of alumina and raw bauxite, accounting for more than 40% of global consumption. Other large aluminium markets are the United States of America, Japan and Europe but these regions possess few economic bauxite deposits and also rely on imports for their aluminium smelters. In 2014, Australia produced the seventh highest amount of aluminium in the world after China, Russia, Canada, the United Arab Emirates, India and the United States of America. Australian bauxite, alumina and aluminium statistics are published each year by the Office of the Chief Economist.

Mining Extraction of aluminium metal takes place in three main stages - mining of bauxite ore, refining the ore to recover alumina and smelting alumina to produce aluminium. Mining Bauxite is mined by surface methods (open-cut mining) in which the topsoil and overburden are removed by bulldozers and scrapers. The topsoil is then stored and later used for revegetating and restoring the area after mining is completed. The underlying bauxite is mined by front-end loaders, power shovels or hydraulic excavators. Some bauxite ores are merely crushed, dried and shipped. Other bauxite is beneficiated after crushing by washing to remove some of the clay, reactive silica and sand waste and then dried in rotary kilns. The ore is then loaded into trucks, railway cars or onto conveyor belts and transported to ships or refineries. Refining In almost all commercial operations, alumina is extracted from the bauxite by the Bayer refining process. The process, discovered by Karl Josef Bayer in 1888, consists of four stages. Digestion - in which the finely ground bauxite is fed into a steam-heated unit called a digester.

Here it is mixed, under pressure, with a hot solution of caustic soda. The aluminium oxide of the bauxite (and the reactive silica) reacts with the caustic soda forming a solution of sodium aluminate or green liquor and a precipitate of sodium aluminium silicate. Clarification - in which the green liquor or alumina-bearing solution is separated from the waste (the undissolved iron oxides and silica which were part of the original bauxite and now make up the sand and red mud waste). This stage involves three steps: firstly, the coarse sand-sized waste is removed and washed to recover caustic soda; secondly, the red mud is separated out; and, thirdly the remaining green liquor is pumped through filters to remove any residual impurities. The sand and mud are pumped together to residue lakes and the green liquor is pumped to heat exchangers where it is cooled from 1000°C to around 650-790°C. Precipitation - in this stage, the alumina is precipitated from the liquor as crystals of alumina hydrate.

To do this, the green liquor solution is mixed in tall precipitator vessels with small amounts of fine crystalline alumina, which stimulates the precipitation of solid alumina hydrate as the solution cools. When completed the solid alumina hydrate is passed on to the next stage and the remaining liquor, which contains caustic soda and some alumina, goes back to the digesters. Calcination - in the final stage, the alumina hydrate is washed to remove any remaining liquor and then dried. Finally, it is heated to about 1000°C to drive off the water of crystallisation, leaving the alumina, which is a dry, pure white, sandy material. A portion of the alumina may be left in the hydrate form or further processed for the chemical industry. Smelting All commercial production of aluminium is based on the Hall-Héroult smelting process in which the aluminium and oxygen in the alumina are separated by electrolysis. This consists of passing an electric current through a molten solution of alumina and natural or synthetic cryolite (sodium aluminium fluoride).

The molten solution is contained in reduction cells or pots which are lined at the bottom with carbon (the cathode) and are connected in an electrical series called a potline. Inserted into the top of each pot are carbon anodes, the bottoms of which are immersed in the molten solution. The passage of an electric current causes the oxygen from the alumina to combine with the carbon of the anode forming carbon dioxide gas. The remaining molten metallic aluminium collects at the cathode on the bottom of the pot. Periodically, it is siphoned off and transferred to large holding furnaces. Impurities are removed, alloying elements added and the molten aluminium is cast into ingots. The smelting process is a continuous one. As the alumina content of the cryolite bath is reduced more is added. Heat generated by the passage of the electric current maintains the cryolite bath in its molten state so that it will dissolve the alumina. A great amount of energy is consumed during the smelting process; from 14,000 - 16,000 kilowatt hours of electrical energy is needed to produce one tonne of aluminium from about two tonnes of alumina.

The availability of cheap electricity is therefore essential for economic production. Aluminium ingots are produced in various shapes and sizes depending on their end use. They may be rolled into plate, sheet, foil, bars or rods. They may be drawn into wire which is stranded into cable for electrical transmission lines. Presses extrude the ingots into hundreds of different useful and decorative forms or fabricating plants may convert them into large structural shapes. A number of factors in the aluminium production cycle relate to the environment and considerable resources are allocated to minimise the impact of mining, refining and smelting on the surrounding environment. Mine rehabilitation is carried out, making every effort to return the area to at least its original condition. Extreme care is taken also with the handling and disposal of red mud from the refineries. This is usually pumped into dams which are sealed with impervious material to prevent pollution of the surrounding countryside. Strict measures are taken also to minimise fluoride emissions from smelters and dusty or corrosive material from the refineries. Uses The production of alumina consumes more than 90% of the world's production of bauxite. The remainder is used by the abrasive, refractory, and chemical industries.

Bauxite is used also in the production of high-alumina cement, as an absorbent or catalyst by the oil industry, in welding rod coatings and fluxes and as a flux in making steel and ferroalloys. Uses of aluminium include the following: - electrical equipment; car, ship, aircraft construction; metallurgical and chemical processes; domestic and industrial construction; packaging (aluminium foil, cans); kitchen utensils (cutlery, pans). The aluminium industry initiated the development of technology for recycling aluminium containing material and for setting up its own drink can collection centres. One of the industry's main incentives has been the reduced amount of energy it takes to produce one tonne of secondary aluminium compared with one tonne of primary aluminium. This involves a saving of 95% of the energy required to produce molten aluminium from bauxite. Each tonne of recycled aluminium also means a saving of seven tonnes of bauxite. Suggestions for Further Reading Blainey, G.L. 2003 The Rush That Never Ended: A History of Australian Mining, 5th edition, Melbourne University Press, Melbourne. Coghill, I. 1971 Australia's Mineral Wealth, Sorrett, Melbourne.

Ferenczi, P.A. 2001. Iron ore, manganese and bauxite deposits of the Northern Territory. Northern Territory Geological Survey. Report 13. Hughes, F.E. (Ed) 1990 Geology of the Minerals Deposits of Australia and Papua New Guinea, Volumes 1 and 2. The Australasian Institute of Mining and Metallurgy, Melbourne. Aluminium production process Read more How aluminium is produced The pure form of aluminium does not naturally occur in nature, so remained largely unknown until as recently as 200 years ago. Creating aluminium using electricity was first developed in 1886 and is still used to this day. BAUXITE MINING The aluminium production process starts with the mining of bauxites, an aluminium rich mineral in in the form of aluminium hydroxide. About 90% of global bauxite supply is found in tropical areas. ALUMINA PRODUCTION Bauxite is crushed, dried and ground in special mills where it is mixed with a small amount of water. This process produces a thick paste that is collected in special containers and heated with steam to remove most of the silicon present in bauxites.

The ore is loaded into autoclaves and treated with lime–caustic soda. Aluminium oxide appears in the resulting slurry while all the admixtures settle to the bottom as red mud. The sodium aluminate solution is stirred in precipitators for several days, eventually pure alumina or Al2O3 settles at the bottom. REDUCTION PROCESS At an aluminium smelter, alumina is poured into special reduction cells with molten cryolite at 950℃. Electric currents are then induced in the mixture at 400 kA or above; this current breaks the bond between the aluminium and oxygen atoms resulting in liquid aluminium settling at the bottom of the reduction cell. PRIMARY ALUMINIUM Primary aluminium is cast into ingots and shipped to customers or used in the production of aluminium alloys for various purposes. ALUMINIUM ALLOYS The process where the aluminium is shaped to its required form. This process is used for making the vast majority of aluminium products from spectacle frames, telephone bodies, aeroplane fuselages or spaceship bodies. The malleability of aluminium means it can be easily rolled into thin sheets.

To that end, aluminium alloys are cast into rectangular beams up to 9 metres in length, these are then rolled into sheets from which aluminium foil and beverage cans are made, as well as parts of automobile bodies and a vast array of other products. The process where the aluminium is shaped to its required form. This process is used for making the vast majority of aluminium products from spectacle frames, telephone bodies, aeroplane fuselages or spaceship bodies. RECYCLING Unlike iron, aluminium is corrosion resistant so it can be remelted and reused an infinite number of times. The added benefit is that recycling aluminium requires only 5% of the energy needed to make the same amount of primary aluminium. How aluminium is produced The pure form of aluminium does not naturally occur in nature, so remained largely unknown until as recently as 200 years ago. Creating aluminium using electricity was first developed in 1886 and is still used to this day. Bauxite mining BAUXITE MINING The aluminium production process starts with the mining of bauxites, an aluminium rich mineral in in the form of aluminium hydroxide. About 90% of global bauxite supply is found in tropical areas.

Crushing ALUMINA PRODUCTION Bauxite is crushed, dried and ground in special mills where it is mixed with a small amount of water. This process produces a thick paste that is collected in special containers and heated with steam to remove most of the silicon present in bauxites. Digestion The ore is loaded into autoclaves and treated with lime–caustic soda. Aluminium oxide appears in the resulting slurry while all the admixtures settle to the bottom as red mud. Precipitation The sodium aluminate solution is stirred in precipitators for several days, eventually pure alumina or Al2O3 settles at the bottom. Electrolytic reduction REDUCTION PROCESS At an aluminium smelter, alumina is poured into special reduction cells with molten cryolite at 950⁰С. Electric currents are then induced in the mixture at 400 kA or above; this current breaks the bond between the aluminium and oxygen atoms resulting in liquid aluminium settling at the bottom of the reduction cell. Casting PRIMARY ALUMINIUM Primary aluminium is cast into ingots and shipped to customers or used in the production of aluminium alloys for various purposes.

Foundry alloys ALUMINIUM ALLOYS Foundry aluminium alloys are used to make finished goods by casting the alloys into special moulds. The required properties are given to the metal by adding various admixtures such as silicon, copper or magnesium. These alloys are used in the manufacture of automobile and aviation engines and aluminium alloy wheels. Rolling The malleability of aluminium means it can be easily rolled into thin sheets. To that end, aluminium alloys are cast into rectangular beams up to 9 metres in length, these are then rolled into sheets from which aluminium foil and beverage cans are made, as well as parts of automobile bodies and a vast array of other products. Extrusion The process where the aluminium is shaped to its required form. This process is used for making the vast majority of aluminium products from spectacle frames, telephone bodies, aeroplane fuselages or spaceship bodies. Recycling RECYCLING Unlike iron, aluminium is corrosion resistant so it can be remelted and reused an infinite number of times. The added benefit is that recycling aluminium requires only 5% of the energy needed to make the same amount of primary aluminium.

Aluminum >> Extraction - Bauxite Extraction The first step in extracting aluminum is to remove it from the Earth in mining. This is relatively simple given the abundance of the material. However aluminum is never found isolated in the Earth (due to its reactivity) but instead it is found bound to other elements in compounds. This means that aluminum alone in can never be dug up, but compounds of it, often containing oxygen and silicon, are. Bayer process on industrial scale (click image for enlargement) The bauxite then has to be purified using the Bayer process, whose development changed the course of aluminum's history . The process occurs in two main steps. Firstly the aluminum ore is mixed with the sodium hydroxide in which the oxides of aluminum and silicon will dissolve, but other impurities will not. These impurities can then be removed by filtration. Carbon dioxide gas is then bubbled through the remaining solution, which forms weak carbonic acid neutralising the solution and causing the aluminum oxide to precipitate, but leaving the silicon impurities in solution. After filtration, and boiling to remove water, purified aluminum oxide can be obtained.

The Hall Heroult Process (click image for enlargement) Once purified aluminum oxide has been manufactured aluminum can be removed from it by the Hall-Heroult Method. In this the aluminum oxide is mixed with cryolite (made of sodium fluoride and aluminum fluoride) and then heated to about 980 �C to melt the solids. This is much lower than the temperature required to melt pure aluminum oxide so much energy is saved. The molten mixture is then electrolysed with a very large current and the aluminum ions are reduced to form aluminum metal (at the cathode) and oxygen gas is formed at the anode, where it reacts with the carbon the anode is made from to give carbon dioxide gas. As the process is so long and requires so much energy (in electricity) the aluminum metal obtained is quite expensive, but still it is competitively priced in relation to other metals unlike earlier in its history . Summary: Aluminum is extracted from the ground in compounds, it is the purified to alumina (aluminum oxide) in the bayer process, and the metal is finally obtained after electrolysis in a cryolite solution. The full process needs a lot of energy and is quite expensive. Continue to the Next Section...

Alloys → No notes for this page. uses bauxite powder pdf - Gold Ore Crusher uses bauxite powder pdf Scribd.com – Aluminium The aluminium oxide (a white powder) is obtained by refining bauxite in the Bayer process of Karl Bayer. PDF generated using the open source mwlib toolkit. Code.pediapress.com/ for more information PDF generated at: Mon, 05 Dec 2011 00:43:24 UTC. Aluminium – Wikipedia The chief ore of aluminium is bauxite. Owing to its resistance to corrosion, aluminium is one of the few metals that retain silvery reflectance in finely powdered form, making it an important component of silver-colored paints. Almost all metallic aluminium is produced from the ore bauxite (AlO x (OH)3–2 x ).

Free PDF Access – Materials Count – The Case For Material Flows Analysis The even- tual effectiveness of the policies will depend on whether current analyses of mercury stocks and flows, which have significant uncertainty, are ac- curate STUDY AND REPORT Understanding how to make the most economically and environmen- tally efficient use of materials will require an understanding of the flow… Public Health Statement – ATSDR – Aluminum Aluminum as the metal is obtained from aluminum-containing minerals, primarily bauxite. Powdered aluminum metal is often used in explosives and fireworks. The use of breathing masks and controls on the levels of dust in factories have largely eliminated this problem. Hall Process – Production and Commercialization of Aluminum – National Historic Chemical Landmark Because manufacturers were reluctant to use an unfamiliar metal, the company developed prototype products such as the first cast aluminum tea kettle for use as sales tools. Mining bauxite Four tons of bauxite produce one ton of aluminum—enough to make the cans for more than 60,000 soft drinks.

Global Business Strategic Report – Research and Markets – Aluminum 2 ALUMINUM MARKET II-4 Present Scenario and Outlook II-4 Emerging Markets to be the Key Drivers for Demand Growth II-4 Aluminum Consumption Tilted towards Consumer Applications II-4 Table 2: Global Aluminum Demand by End-Use Sector (2011): Percentage Breakdown of Volume Consumption for Transportation, Packaging& Consum… UFDC – A Brief History of Packaging CITATION PDF VIEWER. The use of flexible packaging materials began with the Chinese, They used sheets of treated mulberry bark to wrap foods as early as the first or second century B.C. An important step for the use of paper in packaging came with the development of paper bags. theanke's posterous – Filed under 'VedantaAGM' "This is at least 100 times more than what was donated in 2011 use of shareholder funds as a donation for political parties is questionable use of shareholders' money," it added. GlobalSpec – Portland Cement Lime Mortar – Products & Suppliers on GlobalSpec Clinker is a fused mineral or mineral mixture, such as alumina or bauxite and lime, which is crushed into a fine powder Search by Specification Learn More.

Portland cement is a hydraulically-setting material that uses the hydration reaction of a salt to form a bond. New World Encyclopedia – Aluminum The aluminum oxide (a white powder) is obtained by refining bauxite in the Bayer process. Its main ore is bauxite. Whether measured in terms of quantity or value, the global use of aluminum exceeds that of any other metal except iron, and it is important in virtually all segments of the world economy. Mining and Refining Aluminum - How Aluminum Works | HowStuffWorks Mining and Refining Aluminum Prev Next Aluminum isn't found in nature as a pure element. It exhibits relatively high chemical reactivity, which means it tends to bond with other elements to form compounds. More than 270 minerals in Earth's rocks and soils contain aluminum compounds. This makes aluminum the most abundant metal and the third most abundant element in Earth's crust. Only silicon and oxygen are more common than aluminum. The next most common metal after aluminum is iron, followed by magnesium, titanium an­d manganese.­ The primary s­ource of aluminum is an ore known as bauxite. An ore is any naturally occurring solid m­aterial from which a metal or valuable mineral can be obtained.

In this case, the solid material is a mixture of hydrated aluminum oxide and hydrated iron oxide. Hydrated refers to water molecules that are chemically bound to the two compounds. The chemical formula for aluminum oxide is Al2O3. The formula for iron oxide is Fe2O3­. Deposits of bauxite occur as flat layers lying near the Earth's surface and may cover many miles. Geologists locate these deposits by prospecting -- taking core samples or drilling in soils suspected of containing the ore. By analyzing the cores, scientists are able to determine the quantity and quality of the bauxite. Luis Castaneda/Getty Images An aerial view of a bauxite mine and alumina processing plant in Australia ­After th­e ore is discovered, open-pit mines typically provide the bauxite that will eventually become aluminum. First bulldozers clear land above a depos­it. Then workers loosen the soil with explosives, which bring the ore to the surface. Giant shovels then scoop up the bauxite-rich soil and dump it into trucks, which carry the ore to a processing plant. ­ France was the first site of large-scale bauxite mining.

In the United States , Arkansas was a major supplier of bauxite before, during and after World War II . But today, the material is predominantly mined in Australia , Africa , South America and the Caribbean. The first step in the commercial production of aluminum is the separation of aluminum oxide from the iron oxide in bauxite. This is accomplished using a technique developed by Karl Joseph Bayer, an Austrian chemist, in 1888. In the Bayer process, bauxite is mixed with caustic soda, or sodium hydroxide, and heated under pressure. The sodium hydroxide dissolves the aluminum oxide, forming sodium aluminate. The iron oxide remains solid and is separated by filtration. Finally, aluminum hydroxide introduced to the liquid sodium aluminate causes aluminum oxide to precipitate, or come out of solution as a solid. These crystals are washed and heated to get rid of the water. The result is pure aluminum oxide, a fine white powder also known as alumina. ­Alumina is a handy material in its own right. Its hardness makes it useful as an abrasive and as a component in cutting tools. It can also be used to purify water and to make ceramics and other building materials.

But its primary use is to act as a starting point to extract pure aluminum. In the next section, we'll see look at the steps required to transform alumina into aluminum. Up Next

Question: Which metal is obtained from the ore bauxite
Answer: Aluminium